Frequency reconfigurable MIMO antenna

Abstract

The invention belongs to the technical field of antennas, and relates to a frequency reconfigurable MIMO antenna, which comprises a dielectric layer, a radiation layer arranged on the upper surface of the dielectric layer and a floor layer arranged on the lower surface of the dielectric layer, the radiation layer comprises two radiation units, so that the antenna forms an MIMO antenna; the radiation unit comprises a radiation patch and a microstrip line connected with the radiation patch; the radiation patch is of a 9-shaped structure, the two 9-shaped structures are distributed in an axial symmetry mode, and openings of the two 9-shaped structures are arranged in a back-to-back mode. The closed end of the 9-shaped structure is provided with a diode and an air band gap so as to realize frequency reconfiguration. According to the invention, frequency reconfiguration of the MIMO antenna can be realized.

Description

Technical Field

[0001] The present application relates to the field of antenna technology, and in particular to a frequency reconfigurable MIMO antenna. Background Art

[0002] With the rapid development of modern radio equipment and communication systems, the demand for the number of antennas on platforms such as aircraft, ships, and satellites is growing. This trend not only significantly expands the space occupied by antennas and increases the quality and manufacturing cost of communication systems, but also further aggravates the problem of deterioration of the electromagnetic environment. Therefore, how to achieve high-efficiency transmission and improve system performance under limited spectrum resources has become a key topic in modern antenna research.

[0003] Therefore, MIMO antennas came into being and gradually became one of the core technologies in the field of 5G wireless communications. In the existing technology, MIMO antennas are composed of multiple independent antenna units, which can improve communication capacity and frequency utilization, and have made important contributions to the development of modern communications.

[0004] However, with the rapid development of communication systems in recent years, spectrum resources have gradually decreased. The rapid increase in the number of antennas has led to a more serious deterioration of electromagnetic compatibility, and the requirements of equipment for antennas have become higher and higher. In this context, how to further improve transmission efficiency has become a hot research issue. Summary of the invention

[0005] Based on this, it is necessary to provide a frequency reconfigurable MIMO antenna to address the above technical issues, which can realize the frequency reconfiguration of the MIMO antenna and improve the transmission efficiency.

[0006] A frequency reconfigurable MIMO antenna comprises: a dielectric layer, a radiation layer arranged on the upper surface of the dielectric layer, and a floor layer arranged on the lower surface of the dielectric layer; The radiation layer includes: two radiation units, so that the antenna forms a MIMO antenna; The radiation unit includes: a radiation patch and a microstrip line connected to the radiation patch; The radiation patch is in a "9" structure, with two "9" structures axially symmetrically distributed and the openings arranged back to back; a diode and an air band gap are provided on the closed end of the "9" structure to achieve frequency reconfiguration.

[0007] In one embodiment, the "9"-shaped structure includes: a first part, a second part, and a third part, all of which are "L"-shaped structures; One end of the first part is connected to one end of the second part, the other end of the first part is connected to one end of the third part via a diode, an air band gap is provided between the other end of the second part and one end of the third part, and the other end of the third part is connected to the microstrip line.

[0008] In one embodiment, the straight line where the other end of the second portion lies is not colinear with the straight line where one end of the third portion lies.

[0009] In one embodiment, a distance between the first portion and a short side of the dielectric layer is smaller than a distance between the third portion and the short side of the dielectric layer.

[0010] In one embodiment, the microstrip line is connected to a position on the third portion close to the other end. In one embodiment, the floor layer is disposed on the lower surface of the dielectric layer at a position corresponding to the microstrip line, and the floor layer is a rectangular structure with three sides collinear with the dielectric layer.

[0011] In one embodiment, a decoupling structure is further provided on the lower surface of the dielectric layer; The decoupling structure includes: a first component connected to the floor layer; The first component is a "T"-shaped structure, and the "T"-shaped structure is arranged at a position corresponding to the symmetry axis on the radiation layer.

[0012] In one embodiment, the “T”-shaped structure includes: a first section and a second section; One end of the first section is connected to the floor layer, and the other end is vertically connected to the midpoint of the second section.

[0013] In one embodiment, the decoupling structure further comprises: a second component disposed on the floor layer; The second component is two "L"-shaped grooves axially symmetrically distributed about the first component; The "L"-shaped groove includes: a first section and a second section; the first section is adjacent to and parallel to the first section; the second section is perpendicular to the first section.

[0014] In one embodiment, the width of the first component is equal to the width of the radiating patch.

[0015] The above-mentioned frequency-reconfigurable MIMO antenna is designed with a radiation layer, which can control the operating frequency by controlling the switching state of the PIN diode, dynamically adjust the resonant frequency of the antenna, and make the antenna work in the desired two modes and three frequency bands, realize three-band resonant operation and frequency reconfiguration, thereby improving the channel width of the antenna, having the ability to cover many air interface standards of wireless communication, better improving the utilization rate of spectrum resources, realizing high-efficiency radiation and transmission under limited spectrum resources, and having good omnidirectional radiation performance, which can meet the needs of different communication scenarios. At the same time, a decoupling structure is also designed, which can improve the isolation between antenna units, reduce the strong electromagnetic coupling between units, reduce the envelope correlation coefficient, ensure the normal working performance of the antenna and good decoupling effect, and realize miniaturization at the same time, achieve good communication effect, thereby ensuring the efficiency and stability of the entire communication system. Compared with the existing technology in which the mutual influence between antenna units is also strengthened when the antenna size is small, this application has significant advantages. In addition, the MIMO antenna of the present application is designed with a printed monopole antenna as the antenna unit, which is light in weight, small in size, low in cost, compact in structure, and simple to manufacture. It can be widely used in wireless communication system terminals, especially in radio equipment detection, satellite communication, mobile communication and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an overall schematic diagram of a frequency reconfigurable MIMO antenna in one embodiment; Figure 2 is a schematic diagram of a radiating unit of a frequency reconfigurable MIMO antenna in one embodiment; Figure 3 is a schematic diagram of a decoupling structure of a frequency reconfigurable MIMO antenna in an embodiment; Figure 4 An equivalent circuit model of a diode of a frequency reconfigurable MIMO antenna in an on state in an embodiment; Figure 5 An equivalent circuit model of a diode of a frequency reconfigurable MIMO antenna in a cut-off state in an embodiment; Figure 6 A surface current distribution diagram of a radiation unit of a frequency reconfigurable MIMO antenna in an embodiment at a resonant frequency of 3.67 GHz before a diode is loaded; Figure 7 A surface current distribution diagram of a radiation unit of a frequency reconfigurable MIMO antenna in an embodiment at a resonant frequency of 5.30 GHz before loading a diode; Figure 8A surface current distribution diagram of a radiation unit of a frequency reconfigurable MIMO antenna in one embodiment in mode 1 (resonance frequency 3.67 GHz) after loading a diode; Fig. 9 A surface current distribution diagram of a radiation unit of a frequency reconfigurable MIMO antenna in one embodiment in mode 1 (resonance frequency 5.30 GHz) after loading a diode; Fig.10 A surface current distribution diagram of a radiation unit of a frequency reconfigurable MIMO antenna in an embodiment in mode 2 (resonance frequency 4.87 GHz) after loading a diode; Fig.11 A schematic diagram of the dimensions of a frequency reconfigurable MIMO antenna in one embodiment; Fig.12 is another schematic diagram of the dimensions of a frequency reconfigurable MIMO antenna in one embodiment; Fig.13 is an S-parameter diagram of a frequency reconfigurable MIMO antenna in a mode according to an embodiment; Fig.14 is an S-parameter diagram of a frequency-reconfigurable MIMO antenna in mode 2 in one embodiment; Fig.15 is a peak gain diagram of a frequency reconfigurable MIMO antenna in two modes in one embodiment; Fig.16 is a diagram of antenna efficiency of a frequency reconfigurable MIMO antenna in two modes in one embodiment; Fig.17 is an envelope correlation coefficient diagram of a frequency reconfigurable MIMO antenna in two modes in one embodiment; Fig.18 is a diversity gain diagram of a frequency reconfigurable MIMO antenna in two modes in one embodiment; Fig.19 is a far-field two-dimensional radiation pattern of a frequency reconfigurable MIMO antenna in mode 1 (resonance frequency 3.67 GHz) in one embodiment; Fig. 20 is a far-field two-dimensional radiation pattern of a frequency reconfigurable MIMO antenna in mode 1 (resonant frequency 5.30 GHz) in one embodiment; Fig.21 1 is a far-field two-dimensional radiation pattern of a frequency reconfigurable MIMO antenna in mode 2 (resonant frequency 4.87 GHz) in an embodiment.

[0017] Reference numerals: Dielectric layer 1; Radiation layer 2, radiation patch 21, first part 211, second part 212, third part 213, microstrip line 22, diode 23, air band gap 24; Floor layer 3 , first component 31 , first section 311 , second section 312 , second component 32 , first node 321 , second node 322 . DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0019] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0020] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "multiple groups" means at least two groups, such as two groups, three groups, etc., unless otherwise clearly and specifically defined.

[0021] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0022] In addition, the technical solutions between the various embodiments of the present application can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0023] The present application provides a frequency reconfigurable MIMO antenna, such as Figures 1 to 3 As shown, in one embodiment, it includes: a dielectric layer, a radiation layer and a floor layer. The dielectric layer is a supporting component, providing a bearing space for the radiation layer and the floor layer; specifically, the dielectric layer is a rectangular structure, and two radiation units of the radiation layer are arranged in a mirror image.

[0024] The radiation layer is a radiation component, which is arranged on the upper surface of the dielectric layer, and includes: two radiation units, so that the antenna forms a MIMO antenna; the radiation unit includes: a radiation patch and a microstrip line, and the two ends of the microstrip line are respectively connected to the radiation patch and the edge of the dielectric layer; the radiation patch is in a "9" structure, the two "9" structures are axially symmetrically distributed, and the openings of the two "9" structures are arranged back to back; a diode (such as a PIN diode) and an air band gap are provided on the closed end of the "9" structure, which can support different current paths to achieve resonance in different frequency bands and frequency reconfiguration, and improve the resonance depth and resonance frequency of the frequency.

[0025] The floor layer is a grounding component and is arranged on the lower surface of the dielectric layer.

[0026] Preferably, the "9" structure includes: a first part, a second part and a third part; the first part, the second part and the third part are all "L" shaped structures and are arranged in sequence; specifically: one end of the first part is connected to one end of the second part, the other end of the first part is connected to one end of the third part through a diode, an air band gap is provided between the other end of the second part and one end of the third part, and the other end of the third part is connected to a microstrip line. The above arrangement can achieve dual-frequency resonance and increase the resonance depth.

[0027] Further preferably, the straight line where the other end of the second part is located is not collinear with the straight line where one end of the third part is located, so as to improve S 11 performance, increasing resonance depth.

[0028] More preferably, the distance between the first portion and the short side of the dielectric layer is smaller than the distance between the third portion and the short side of the dielectric layer, so as to further increase the resonance depth.

[0029] More preferably, the microstrip line is connected to a position on the third part near the other end, and in the horizontal and vertical directions, the distance between the microstrip line and the first part is smaller than the distance between the microstrip line and the second part, so as to change the current path of the electromagnetic wave, ensure the resonance depth and resonance frequency at the high frequency when the PIN diode is turned on, and realize multi-band operation.

[0030] In another embodiment, the floor layer is disposed on the lower surface of the dielectric layer at a position corresponding to the microstrip line, and the floor layer is a rectangular structure with three sides colinear with the dielectric layer to achieve grounding and increase impedance matching of the monopole antenna.

[0031] Preferably, the length of the floor layer is equal to the length of the dielectric layer, the width of the floor layer is smaller than the width of the dielectric layer, the width of the floor layer is greater than the length of the microstrip line, and the floor layer partially overlaps with the third part of the radiation patch to ensure the resonant frequency of multiple bands, especially the resonant frequency at low frequencies, and expand the resonant frequency band.

[0032] In another embodiment, a decoupling structure is further provided on the lower surface of the dielectric layer; the decoupling structure comprises: a first component connected to the floor layer; the first component is a "T"-shaped structure, and the "T"-shaped structure is provided at a position corresponding to the symmetry axis on the radiation layer. The provision of the first component can add an additional current path, effectively reduce the current flow from the excitation port to the non-excitation port, and improve the isolation between the radiation units.

[0033] Preferably, the "T"-shaped structure includes: a first section and a second section; one end of the first section is connected to the floor layer, and the other end is vertically connected to the midpoint of the second section to further provide an additional shunt path, effectively reduce the mutual coupling effect, and filter out the coupling current on the floor layer.

[0034] Further preferably, the length of the first section is greater than the length of the second section, so as to increase the resonance depth and improve the isolation of the antenna at low frequencies.

[0035] More preferably, the decoupling structure further includes: a second component disposed on the floor layer; the second component is two "L"-shaped grooves axially symmetrically distributed about the first component; the "L"-shaped groove includes: a first section and a second section; the first section is adjacent to and parallel to the first segment, and the length of the first section is less than the width of the floor layer; the second section is perpendicular to the first section, that is, the second section is perpendicular to the first segment, and the second section is parallel to the second segment; the widths of the first segment, the second segment, the first section, and the second section are all equal. The arrangement of the second component can filter out the surface wave current on the floor, thereby further improving the isolation between the two antenna units and achieving high isolation of the antenna.

[0036] More preferably, the length of the second section is greater than that of the first section, and the length of the second section is greater than that of the second section, so as to avoid coupling with the radiation patch, increase the high-frequency resonance frequency and depth, and maintain good isolation of the antenna at both low and high frequencies.

[0037] More preferably, the width of the first component is equal to the width of the radiation patch (each part of the radiation patch is of equal width) to improve the coupling of the antenna, avoid the generation of new resonance modes, maintain the continuity of the electromagnetic field distribution, and ensure the resonance depth.

[0038] In the present application, under different working states of the PIN diode, its circuit characteristics are different.

[0039] like Figure 4 and Figure 5As shown in the figure, when the PIN diode is turned on, it can be equivalent to an RL series resonant circuit with an inductor and a resistor in series, and when it is turned off, it can be equivalent to an RLC parallel resonant circuit with a resistor and a capacitor in parallel and then in series with an inductor. Based on this characteristic of the PIN diode, changing the voltage across the PIN diode can change the on-off state of the PIN diode, thereby changing the structure of the antenna, distributing the current in different parts, and realizing the reconfiguration of the antenna.

[0040] Table 1 shows different mode combinations caused by the switching state of the PIN diode. When using simulation software to simulate the working state of the PIN diode, a very small resistor can be used to be equivalent to the forward bias state of the PIN diode, and a high-resistance capacitor can be used to be equivalent to the reverse bias state of the PIN diode to simulate the conduction and cutoff of the PIN diode.

[0041] Table 1: Different mode combinations resulting from PIN diode switching states

[0042] like Figure 6 and Figure 7 As shown, analysis shows that when the antenna works at 3.67GHz, the current intensity of the horizontal section of the second part and the vertical section of the third part on the antenna radiation patch is relatively large, which is consistent with the characteristics of long resonant branches in the low frequency band; when the antenna is switched to 5.30GHz, the current intensity of the third part on the antenna radiation patch is relatively large, which is consistent with the characteristics of short resonant branches in the high frequency band. It can be seen that the current distribution intensity at the edge of the branch at the two resonant frequencies is larger than that of other parts, and it is also particularly obvious at the turning point of the branch. This is because the electromagnetic waves radiated by the microstrip antenna generally come from non-continuous parts such as the turning point of the oscillator, the open port or the mutation; in addition, the current distribution shown in the figure also confirms the 3.67GHz and 5.30GHz λ / 4 The current path lengths are 21.35mm and 13.15mm respectively. High frequencies are generated by shorter antenna branches, and low frequencies are generated by longer antenna branches, which are consistent with the size range of theoretical calculations (the specific theoretical calculations belong to the prior art).

[0043] like Figure 8 and Fig. 9 As shown in Figure 1, the surface current distribution of the radiating unit in dual frequency mode 1 is Figure 6 as well as Figure 7 resemblance.

[0044] like Fig.10As shown, in Mode 2, since the PIN diode disconnects the capacitor equivalent to a high resistor, it prevents the current from flowing to the long low-frequency oscillator. The current is mainly distributed in the high-frequency oscillator part. Therefore, in Mode 2, the antenna only resonates at a frequency of 4.87 GHz.

[0045] The above-mentioned frequency-reconfigurable MIMO antenna is designed with a radiation layer, which can control the operating frequency by controlling the switching state of the PIN diode, dynamically adjust the resonant frequency of the antenna, and make the antenna work in the desired two modes and three frequency bands, realize three-band resonant operation and frequency reconfiguration, thereby improving the channel width of the antenna, having the ability to cover many air interface standards of wireless communication, better improving the utilization rate of spectrum resources, realizing high-efficiency radiation and transmission under limited spectrum resources, and having good omnidirectional radiation performance, which can meet the needs of different communication scenarios. At the same time, a decoupling structure is also designed, which can improve the isolation between antenna units, reduce the strong electromagnetic coupling between units, reduce the envelope correlation coefficient, ensure the normal working performance of the antenna and good decoupling effect, and realize miniaturization at the same time, achieve good communication effect, thereby ensuring the efficiency and stability of the entire communication system. Compared with the existing technology in which the mutual influence between antenna units is also strengthened when the antenna size is small, this application has significant advantages. In addition, the MIMO antenna of the present application is designed with a printed monopole antenna as the antenna unit, which is light in weight, small in size, low in cost, compact in structure, and simple to manufacture. It can be widely used in wireless communication system terminals, especially in radio equipment detection, satellite communication, mobile communication and other fields.

[0046] In a specific embodiment, Fig.11 and Fig.12 As shown, the dielectric layer is made of FR4 material, and its parameters are εr=4.4, tanδ=0.02, length and width are both 25mm, and thickness H=0.8mm.

[0047] The size parameters are shown in Tables 2 and 3.

[0048] Table 2: Dimensional parameters 1

[0049] Table 3: Dimensional parameters 2

[0050] like Fig.13 and Fig.14 As shown, the S at the resonant frequency in the two modes 11Both are less than -10dB, indicating that the antenna has a better matching effect at the resonant frequency. In Mode 1, the antenna resonates in the dual frequency bands of 3.67GHz and 5.30GHz; in Mode 2, the antenna resonates in the frequency band of 4.87GHz. 21 The value reflects the mutual coupling between antenna units. The S value of the center resonant frequency of the antenna in Mode 1 and Mode 2 is 21 The values ​​are all less than -10dB.

[0051] like Fig.15 As shown, it can be seen that the peak gains of the antenna in its working frequency band are: the peak gain in mode 1 at 3.59~3.72GHz is 3.16~3.48dBi, the peak gain in mode 1 at 5.14~5.55GHz is 4.70~5.08dBi, and the peak gain in mode 2 at 4.45~5.23GHz is 2.01~3.92dBi. The antenna radiation performance is good.

[0052] like Fig.16 As shown, the highest antenna radiation efficiency in the operating frequencies under Mode 1 and Mode 2 reaches 98.01% and 97.33% respectively.

[0053] like Fig.17 As shown, it can be seen that the envelope correlation coefficient (ECC) value of the antenna is kept below 0.03 within the working frequency band. This value is much lower than the 0.5 threshold value usually required for MIMO antennas, indicating that the diversity performance of the MIMO antenna in this application is good.

[0054] like Fig.18 As shown, it can be seen that for the two modes, the diversity gain (DG) values ​​of the antenna in the working frequency band are both within 9.8~10.0dB, showing good diversity benefit.

[0055] like Figures 19 to 21 As shown in the figure, when the antenna works at 5.30 GHz in Mode 1, the radiation patterns of the E and H planes of the antenna are approximately in the shape of an "8", while when working at 3.65 GHz in Mode 1 and 4.87 GHz in Mode 2, the radiation patterns of the E and H planes of the antenna are basically circular, showing omnidirectional radiation characteristics, indicating that the radiation power of the two frequency bands covers the surrounding area well, ensuring the wide coverage and efficient transmission of the antenna signal.

[0056] In summary, the overall size of the antenna of the present application is 25mmx50mm, which can achieve frequency reconfiguration of mode 1 (3.59~3.72GHz, 5.14~5.55GHz) and mode 2 (4.45~5.23GHz), and has a short response delay and a compact design; through frequency reconstruction, the antenna operating frequency band covers the three frequency bands of 3.59~3.72GHz, 5.14~5.55GHz, and 4.45~5.23GHz; when the PIN diode is turned on, the antenna operates in the 3.59~3.72GHz and 5.14~5.55GHz bands, and the resonant frequencies are 3.67GHz and 5.30GHz respectively. The antenna efficiency is as high as 98.01%, and the peak gain of the antenna at the operating frequency is 2.5~3.72GHz. The gain can reach 5.08dBi; when the PIN diode is cut off, the antenna works in the 4.45~5.23GHz band, the resonant frequency is 4.87GHz, the antenna efficiency is as high as 97.33%, and the peak gain of the antenna at the working frequency can reach 3.92dBi; the added decoupling structure improves the isolation by 10dB as a whole, the antenna isolation is better than 10dB in the working frequency band, and the maximum isolation can reach 18dB, with excellent decoupling performance, and high isolation of the antenna; the envelope correlation coefficient of the antenna is less than 0.03 in both working modes, and the diversity gain is within 9.8~10dB. The antenna shows excellent radiation performance as a whole, with high diversity gain and good antenna performance; the antenna radiation pattern is circular, which can achieve omnidirectional radiation. In general, the antenna has the characteristics of simple structure, multiple working frequency bands and high isolation.

[0057] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

[0058] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A frequency reconfigurable MIMO antenna, characterized in that: include: A dielectric layer, a radiation layer disposed on the upper surface of the dielectric layer, and a floor layer disposed on the lower surface of the dielectric layer; The radiation layer includes: two radiation units, so that the antenna forms a MIMO antenna; The radiation unit includes: a radiation patch and a microstrip line connected to the radiation patch; The radiation patch is in a "9" structure, with two "9" structures axially symmetrically distributed and the openings arranged back to back; a diode and an air band gap are provided on the closed end of the "9" structure to achieve frequency reconfiguration.

2. A frequency reconfigurable MIMO antenna according to claim 1, characterized in that: The "9"-shaped structure includes: a first part, a second part and a third part, all of which are "L"-shaped structures; One end of the first part is connected to one end of the second part, the other end of the first part is connected to one end of the third part via a diode, an air band gap is provided between the other end of the second part and one end of the third part, and the other end of the third part is connected to the microstrip line.

3. A frequency reconfigurable MIMO antenna according to claim 2, characterized in that: The straight line where the other end of the second part lies is not collinear with the straight line where one end of the third part lies.

4. The frequency reconfigurable MIMO antenna according to claim 3, characterized in that: The distance between the first portion and the short side of the dielectric layer is smaller than the distance between the third portion and the short side of the dielectric layer.

5. The frequency reconfigurable MIMO antenna according to claim 4, characterized in that: The microstrip line is connected to a position on the third portion close to the other end.

6. A frequency reconfigurable MIMO antenna according to any one of claims 1 to 5, characterized in that: The floor layer is arranged on the lower surface of the dielectric layer at a position corresponding to the microstrip line, and the floor layer is a rectangular structure with three sides collinear with the dielectric layer.

7. A frequency reconfigurable MIMO antenna according to any one of claims 1 to 5, characterized in that: A decoupling structure is also provided on the lower surface of the dielectric layer; The decoupling structure includes: a first component connected to the floor layer; The first component is a "T"-shaped structure, and the "T"-shaped structure is arranged at a position corresponding to the symmetry axis on the radiation layer.

8. The frequency reconfigurable MIMO antenna according to claim 7, characterized in that: The "T"-shaped structure includes: a first section and a second section; One end of the first section is connected to the floor layer, and the other end is vertically connected to the midpoint of the second section.

9. The frequency reconfigurable MIMO antenna according to claim 8, characterized in that: The decoupling structure further includes: a second component disposed on the floor layer; The second component is two "L"-shaped grooves axially symmetrically distributed about the first component; The "L"-shaped groove includes: a first section and a second section; the first section is adjacent to and parallel to the first section; the second section is perpendicular to the first section.

10. The frequency reconfigurable MIMO antenna according to claim 9, characterized in that: The width of the first component is equal to the width of the radiation patch.

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